Malaysia's government has begun investigating civil aviation and military authorities to determine why opportunities to identify and track Malaysia Airlines Flight MH370 were missed in the chaotic hours after it vanished, two officials said.

The preliminary internal enquiries into the Malaysia Airlines MH370 tragedy come as tensions mount between civilian and military authorities over who bears most responsibility for the initial confusion and any mistakes that led to a week-long search in the wrong ocean.

"What happened at that time is being investigated and I can't say any more than that because it involves the military and the government," a senior government official told Reuters.

In an interview with Reuters last weekend, Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said internal enquiries were under way, although he declined to give details.

A government spokesman did not respond to questions over whether an investigation had been launched. The senior government source said it was aimed at getting a detailed picture of the initial response. It was unclear which government department was in charge or whether a formal probe had been opened.

Malaysia's opposition coalition has demanded a parliamentary inquiry into what happened on the ground in those first few hours. Government officials have said any formal inquiry should not begin until the flight's black box recorders are found.

The Malaysia Airlines MH370 Boeing 777 was carrying 227 passengers and 12 crew when it disappeared on March 8. Malaysia says it believes the plane crashed into the southern Indian Ocean after being deliberately diverted from its Kuala Lumpur-to-Beijing route.

A search effort is taking place well out to sea off the Australian city of Perth to try to locate any wreckage as well as the recorders which may provide answers to what happened onboard.

MECHANICAL PROBLEM ASSUMED

Interviews with the senior government source and four other civilian and military officials show that air traffic controllers and military officials assumed the plane had turned back to an airport in Malaysia because of mechanical trouble when it disappeared off civilian radar screens at 1:21 a.m. local time.

That assumption took hold despite no distress call or other communication coming from the cockpit, which could have been a clue that the plane had been hijacked or deliberately diverted.

The five sources together gave Reuters the most detailed account yet of events in the hour after the plane vanished. All declined to be identified due to the sensitivity of the issue and because they were not authorised